The correlation between serum inflammatory, antioxidant, glucose handling biomarkers, and Dietary Antioxidant Index (DAI) and the role of DAI in obesity/overweight causation: population-based case-control study.

BACKGROUND: Obesity is a multifactorial disease, and about 40% of world adults are overweight, and about 20% are obese. Diet is one of the most important factors in the causality of obesity. The interactions between the diet and gut microbiota or chronic inflammation pathways highlight the importance of its various aspects in the incidence and prevalence of obesity. At the same time, diet is a combination of several antioxidants that are needed together for the body's antioxidant system. The Dietary Antioxidant Index (DAI) is a valid nutritional tool, and its correlation has been studied concerning total antioxidant capacity and malondialdehyde. The study aimed to examine the relationship between the DAI and the odds of obesity. We hypothesized that a higher DAI score indicating a predominantly antioxidant diet has a protective effect against odds of obesity. METHODS: In this population-based case-control study, 812 participants with a higher body mass index (BMI) than 25 were selected as the case group. Also, 793 participants with BMI in the range of 17.9-24.9 were selected as the control group. A valid and reliable 124-item food frequency questionnaire (FFQ) was used to assess dietary intake. Based on FFQ data, we summed up the standardized intake of the major dietary antioxidants, including vitamin A, E, C, selenium, zinc, and manganese, to calculate DAI. RESULTS: In a multivariable adjusting model, there was a significant association between DAI (as a continuous variable) and BMI (odds ratio (OR) = 0.95; 95% CI: 0.92-0.99; P value = 0.02). Also, there was a significant association between DAI (as a categorized variable) and body surface area with multivariable adjusting model (OR = 0.79; 95% CI: 0.64-0.98; P value = 0.04). CONCLUSION: In conclusion, the DAI can accurately predict some serum antioxidant and anti-inflammatory levels along with glucose handling markers.